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Spaces of Possibility

Published online by Cambridge University Press:  03 July 2018

Timothy Williamson*
Affiliation:
University of Oxford

Abstract

We care not just how things are but how they could have been otherwise – about possibility and necessity as well as actuality. Many philosophers regard such talk as beyond the reach of respectable science, since observation tells us how things are but (allegedly) not how they could have been otherwise. I argue that, on the contrary, such criticisms are ill-founded: possibility and necessity are studied in natural science, for example through phase spaces, abstract mathematical representations of the possible states of a physical system. The possibility is objective, not merely epistemic, though it may be more restricted than pure metaphysical possibility. The elements of a phase space are very similar to Kripke's possible worlds, despite being time slices rather than total histories. The absence of explicit modal operators in the mathematical models used by scientists does not show science to be non-modal; rather, it manifests reliance on a mathematical framework for theorizing about objective possibility similar to the mathematical framework of possible worlds model theory.

Type
Papers
Copyright
Copyright © The Royal Institute of Philosophy and the contributors 2018 

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References

1 This paper descends from a lecture given at the Royal Institute of Philosophy, where it received useful feedback. For a more detailed and rigorous development of the ideas in it, see Williamson, Timothy, ‘Modal Science’, Canadian Journal of Philosophy 46 (2016): 453492CrossRefGoogle Scholar. More general issues about the status of modal logic are treated in Williamson, Timothy, Modal Logic as Metaphysics (Oxford: Oxford University Press, 2013)CrossRefGoogle Scholar.

2 For the large relevant literature by linguists on the semantics of modal expressions in natural language, one might start with Kratzer, Angelika, ‘What “must” and “can” must and can mean’, Linguistics and Philosophy 1 (1977): 337355CrossRefGoogle Scholar, and Modals and Conditionals: New and Revised Perspectives (Oxford: Oxford University Press), and Paul Portner, Modality (Oxford: Oxford University Press). For an exchange on the distinction between epistemic and objective modalities see Vetter, Barbara, ‘Williamsonian modal epistemology, possibility-based’, Canadian Journal of Philosophy 46 (2016): 766795CrossRefGoogle Scholar, and Williamson, Timothy, ‘Reply to Vetter’, Canadian Journal of Philosophy 46 (2016): 796802CrossRefGoogle Scholar.

3 See Kripke, Saul, Naming and Necessity (Oxford: Blackwell, 1980)Google Scholar.

4 For a strong case for modal perception, see Strohminger, MargotPerceptual knowledge of nonactual possibilities’, Philosophical Perspectives 29 (2015): 363375CrossRefGoogle Scholar.

5 See Gibson, James, The Ecological Approach to Visual Perception (Boston, MA: Houghton Mifflin, 1979)Google Scholar.

6 See especially van Orman Quine, Willard, ‘Reference and modality’, in his From a Logical Point of View (Cambridge, MA: Harvard University Press, 1953): 139159Google Scholar.

7 See Lewis, David, ‘Counterpart theory and quantified modal logic’, Journal of Philosophy 65 (1968): 113126CrossRefGoogle Scholar, and On the Plurality of Worlds (Oxford: Blackwell, 1986)Google Scholar.

8 For a recent exchange on this objection to Lewis's modal realism see Divers, John, ‘Modal reality and (modal) logical space’, Philosophy and Phenomenological Research 88 (2014): 726733CrossRefGoogle Scholar, and Williamson, Timothy, ‘Replies to Bricker, Divers, and Sullivan’, Philosophy and Phenomenological Research 88 (2014): 744764CrossRefGoogle Scholar.

9 For exploration of these issues see Kim, Jaegwon, Supervenience and Mind: Selected Philosophical Issues (Cambridge: Cambridge University Press, 1993)CrossRefGoogle Scholar.

10 See Fine, Kit, ‘Essence and modality’, Philosophical Perspectives, 8 (1994): 116CrossRefGoogle Scholar.

11 See Sider, Ted, Writing the Book of the World (Oxford: Clarendon Press, 2011)CrossRefGoogle Scholar, and On Williamson and simplicity in modal logic’, Canadian Journal of Philosophy 46 (2016): 683698CrossRefGoogle Scholar, and Williamson, Timothy, ‘Reply to Sider’, Canadian Journal of Philosophy 46 (2016): 699708CrossRefGoogle Scholar.

12 See Nolte, David, ‘The tangled tale of phase space’, Physics Today, 63/4 (2010): 3338CrossRefGoogle Scholar.

13 For an introduction to dynamical systems theory, see Strogatz, Steven, Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering (Boulder, CO: Westview: 2001)Google Scholar.

14 See Quine, W.V.O., ‘Three grades of modal involvement’, in his The Ways of Paradox (New York: Random House, 1966): 156174Google Scholar.